1. Field of the Invention
This invention relates to a grommet for sealing a gap between a hole formed in a panel of a vehicle and a wire harness passing through the hole, and more particularly to a grommet which can fit on any one of wire harnesses of different diameters.
2. Related Art
When passing a wire harness through a panel of a vehicle, a grommet is used for preventing water, dust and so on from intruding through a gap between a through hole and the wire harness. One such grommet, disclosed in Japanese Patent Unexamined Publication No. Hei. 8-129918, will be described.
As shown in FIG. 4, this grommet 1 includes an enlarged-diameter portion 3 of a larger-diameter, conical tubular shape for mounting in a hole in a vehicle panel, and a reduced-diameter portion 5 of a smaller-diameter, cylindrical shape extending continuously from a smaller-diameter end of this enlarged diameter portion. An engagement groove 7 is formed in an outer peripheral surface of the enlarged-diameter portion 3, and an inner peripheral edge of the hole is adapted to fit in this engagement groove 7. The inner periphery of the enlarged-diameter portion 3 defines a passage hole 9 for loosely passing a wire harness therethrough. The reduced-diameter portion 5 has a generally conical tubular shape decreasing in diameter progressively toward its distal end from its proximal end continuous with the enlarged-diameter portion 3. Thick ribs 11 are formed on the outer peripheral surface of the reduced-diameter portion 5, and are spaced at predetermined intervals in the axial direction.
If the outer diameter of the wire harness, which is to be passed through the vehicle panel by the use of this grommet 1, is larger than an inner diameter A of the distal end of the reduced-diameter portion 5, the reduced-diameter portion 5 is cut at a required portion thereof by scissors, so that the inner diameter of the reduced-diameter portion 5 is brought into agreement with the outer diameter of the wire harness. Then, the reduced-diameter portion 5 is enlarged in diameter by a grommet-expanding machine, and the wire harness is passed through the grommet, and then an adhesive tape is wound on the reduced-diameter portion 5 and the wire harness, thereby fixing the grommet to the wire harness. In this condition, the engagement hole 7 in the grommet 1 is fitted on the peripheral edge of the vehicle panel, thus completing the assembling operation.
This grommet 1 has the reduced-diameter portion 5 of a generally conical tubular shape decreasing in diameter progressively toward the distal end thereof, and this reduced-diameter portion 5 is cut in accordance with the outer diameter of the wire harness. Therefore, one kind of grommet 1 can be suitably used for wire harnesses of different diameters.
In the above conventional grommet 1, however, that portion of the tapering, reduced-diameter portion, extending from the insertion hole of the minimum diameter A to an insertion hole of a maximum diameter B, is linearly varying. Therefore, in the case of enlarging the diameter of the reduced-diameter portion, the reduced-diameter portion must be enlarged in diameter over a long distance in the axial direction, and therefore a large diameter-enlarging force is required. As a result, there is encountered a problem that the efficiency of the operation is low.
And besides, the reduced-diameter portion must be cut in accordance with the outer diameter of the wire harness, and thus this additional cutting operation is required for the wire harness-passing operation.
Furthermore, there can be produced those grommets which can not be used because of cutting errors or the like.